This invention relates to energy control systems, and more particularly to a control system which can maintain heating and air conditioning systems operating at offset temperatures.
The temperature within a particular premises is generally maintained by means of heating and/or air conditioning systems. In some cases, a central system is utilized which can provide either heating or air conditioning or the combination thereof. In other situations, individual units may be utilized such as room air conditioners or individual heaters. Each of these heating and/or air conditioning systems generally utilize a local thermostat on which can be set the desired temperature to be maintained. For example, the local thermostat may be set at 78.degree. F. and during winter the heating will turn on as the temperature in the inside atmosphere goes below 78.degree. F. and turns off as the temperature goes above 78.degree. F. Some small range of temperature variation is permitted, generally that of a few degrees. The air conditioning units would similarly operate by being controlled to turn on and off by means of their local thermostats.
When a user leaves his premises for the day, it is wasteful to keep the heating and/or air conditioning units functioning at their normal set temperature. For this reason, the individual may lower the temperature setting on the thermostat for his heating units and may raise the temperature setting on the thermostat unit associated with his air conditioning unit. However, this therefore requires continuous daily adjustment of the thermostat before the individual leaves the premises. This is an inconvenience and the individual often tends to forget to adjust the temperature setting. Additionally, since different temperature settings are required for winter and summer, depending upon whether the heating or air conditioning unit is being operated, it may often confuse the individual to remember which way to adjust the thermostat and, he may in fact adjust it in the wrong direction, thereby causing additional energy to be expended while he is away from the premises.
A further problem is that if the individual does readjust the setting on the thermostat when he leaves the premises, by the time he returns home, the house will be either too hot during the summertime or too cold during the winter time. It will then take some length of time after the individual returns until the house can be returned to a comfortable temperature. For this problem, it has been suggested to include a standard timing device into which the air conditioner or heater is plugged, and have the timer set at approximately one hour before the individual plans to return home. One difficulty is that most heating and/or air conditioning units require high voltage and accordingly the clock must be able to accommodate such high voltage, thereby increasing the cost of the clock. Additionally, if each room has its own individual heater and/or air conditioner, this would require several individual clocks for each unit. On the other hand, if a central heating and/or air conditioning system is utilized, it becomes difficult to connect a clock. Such timing device would have to be built directly into the house wiring and thereby presents a problem of cost, maintenance, and continuous resetting of the time when the individual leaves the house. Since the time clock turns the air conditioning and/or heating completely off, substantial discomfort and/or damage might occur in below freezing climates if the heater is turned completely off. Similarly in very hot and humid climates, cooling the premises back down might take hours, if the air conditioning is turned completely off.
Accordingly, there is a need for a suitable energy saving device which can be utilized to provide temperature offset for heating and/or air conditioning systems which is easy to install, simple to utilize, and reduced in cost.